Method for geophysical prospecting



gamut-s r c; A. MOON MayzsJsm.

SUBSTITUTE FOR MLSSlNl XR METHOD POR Geo? gmc@ hf/6MM@ YSICAL PROSPECTING Filed March l2, 1942 2349366 OR IN E50/254 Patented May 23, 1944 unirse spares sieste earner. oserei:

2,349,366 IQETHOD FUR GEOPHYSICL PROSPECTING. Charles A. Moon, Caracas, Venezuela, assignor to mpany, Incorporated,

New York. N. Y.. a corporation o! New York Application Msrchxz, 1942, serial No. 434,421 9 claims. (c1. 25o-83.6)

cality for operations, to drill a well bore in the earth to a depth such that a satisfactorily productive stratum is encountered cr the ncnproductlve nature of the region is definitely established. As experience o workers in this eld indicates. the presence oi productive strata can be predicted with acceptable accuracy after knowledge of the geological character of strata encountered has been obtained by logging the well in accordance with any oi the methods now commonly used. I t will be apparent, accordingly. that the drillimJ and prospecting operations should desirebly be performed simultaneously in order that the drilling crew may be warned of the probable occurrence c-f a productive strata in the vicinity or drilling operoticos, thus permitting them to make ready suitable equipment to prevent waste of discharged oil.

However, most present day methods of geophysical prospectinghaving as enobject to provide dats. indicative oi the character of strata traversed by a well bore are intended to oe or, as a precticalmstter, are performed after the drilling operations have ceased, the drill stem has been removed and the drill operating apparatus has been removed from the mouth of the well bore.

This practice, although very cost-ly because it causes interruption of the drilling schedule and Wastes the time of the drilling crew, is duo to the inherent diicultics, chiey in matters of the design and const. ction oir suitable equipment, that preclude conducting the prospecting operation-s willie the drill stem is in operative position within the bore. Furthermore, many methods of prospetting. based on characteristics oi geological formations such as specic resistivity, chemical analysis, alteration of electrical clds, and the like, widely relied upon by workers in the neld, cannot be performed satisfactorily within 'a metaille sheath such as the drill stem would constitute, thus necessitating previous removal o! the stem and the associated equipment.

Even assuming that suitable equipment were available, an additional dimcuity or c' practical nature makes it undesirable to perform ordinary prospecting operations during drilling oi the well bore because these operations in almost every instance entail the time-consuming procedure ol' lowering the prospecting instrument within the bore at a slow rate of travel adequate for delicate measurements to be obtained with the requisite accuracy and sensitivity. and .thereafter withdrawing the instrument and associated cables from the drill stern. Both of these operations, oi

necessity, would be conducted while the drill stem is chucked on the well bottom and heid motionless in the Well, thus interrupting and delaying the schedule of the drilling crew and materially increasing the expenditures necessary before the productivity or non-productivity of the well could be established with reasonable certainty. For the foregoing and other reasons. the conducting of well logging operations `without removal of the drill siem, although long recognized as being a desirable and economically advantageous procedure. heretoiorehas not been commercially practiced by workers in this field.

The present invention now provides a method of geophysical prospecting that can be practiced during the usual course oi drilling operations without giving rise to delays interrupting the drilling schedule. In practicing the invention. a geophysical prospecting device, preferably of the type sensitive to high frequency radiation, is moved within c. bottom portion of ille well bore et the time of adding each successive new drill stem element to the drill string, thereby providn' ing the operat rs with immediate indications of the character of substrate being traversed by the bore. It thus becomes possible, in accordance with thisy invention. wholly to obviate logging ci the weil subsequent to drilling, thereby efiecting economies not merely during the drilling operations but-also subsequent thereto as the well is being prepared for actual production.

To facilitate a better understanding of the present invention and or how the same may be practiced during field operations, a specific ernbodirnent thereof, presented by way of example but not by way of limitation, will be .hereinafter` described.

In the accompanying drawing the presently preferred embodiment of the instant invention is illustrated, but it is clearly to be understood that the scope of this invention is not to be restricted to this particular embodiment thereof except lnsolar is indicated in the subjoined claims.

Referring to the drawing: Figure 1 is essentially a diagrammatic illustranean formations.

drill bit i2.

` tions.

tion oi a well bore and portions of a well superstructure associated therewith. during an early stage of' drilling and prospecting operations:

Figure 2 is a similar view illustrating a later stage of operations including the addition of a length of drill stem to the partially withdrawn drill string:

gure 3 is a view similar to the foregoing wherein the added length oi drill stem is shown within the well bore and connected into the string; and

Figure 4 is essentially a diagrammatic illustration of a prospecting instrument suitable for employment in the practice oi this invention.

In well drilling operations. additional lengths of drill stem are coupled successively into the drill string as the bit progresses into subterra- These additional drill stem elements are usually introduced into the string by withdrawing the string partially from the well,

both to facilitate attachment ci the new element and to prevent sticking or freezing oi' the bit on the floor oi the well bore, adding the element. and then returning the string to operative position within the well bore. 1n accordance with the present invention, the prospecting operations are conducted while additional stem elements are being incorporated in the drill string as will hereinaiter appear.

. In Figures l, 2, and 3 of the accompanying drawing, a well bore i is illustrated, within which is positioned a drill string ii carrying a The drill string is driven during dr'lling operations by a rotating table i3, coupled to the string through a freely vertically slidable -ielly bar ii, connected to a kelly i5 in the conventional manner. i

In Figure l oi the drawing aninitial stage in the sequence of drilling and prospecting operations according to this invention is illustrated, wherein the drill stem il is shown positioned within the well bore lil with the drilling bit i2, mounted upon the end of the drill string. resting in operative position upon the bottom Iba of the bore. It is to be understood that the Kelly bar ivwhich engagesrwith and is rotated by the table i3, is connected through the kelly i5 to a suitable source of drilling mud in the conventional manner. During the drilling operation the table it is rotated, thereby rotating the drill string and causing it to move downwardlyas the bit, bites through the subterranean earth forma- Tnese operations are continued until the kelly i5 closely approaches the rotating table i3. as illustrated in Figure l. et which time operations are interrupted and the drill stem is partially withdrawn from the well bore for addition of a. further drill stem element to the string.

A second stage in the drilling operations, illustrated in Figure 2. includes the addition oi a length of drill stem to the string as above mentioned. The additional drill stern element i6 is shown attached to the Kelly bar i4, which is permanently connected to the kelly l5 as above described. At this stage oi the operations the drill bit l2 has been raised from the door ia of the well bore i0, both to avoid sticking and to permit introduction o! the additional stem element at the Junction of the Kelly bar and the drill string, and Ls retained in raised position by chucking the string at the rotating table I3. In accordance with the present invention. while the drill string is thus held and before the additional stem element i6 is attached thereto, a

prospecting instrument i'l, hereinafter described, 76

is placed within the string in a manner such that it rests in a preselected position within the stern near the base thereof substantially as shown. AS will be apparent to those versed in this art, the instrument can, if desired, be dropped within th drill stem and permitted to fall lnto the desired position or can be lowered upon a cable, which can be disengaged from the instrument when the same has reached the desired position near the drill bit.

Following the above-described operations. the additional drill siem element is coupled to the portion oi' the drill string held in the rotary table i3 and the assembly then is lowered within the well bore to place the drill bit i2 near its operative position against the bore bottom iba.. inasmuch as the prospecting instrument il remains in its preselected'position within the drill stem during these operations, as the drill string is lowered within the well bore thc instrument is moved from its initial position illustrated in Figure 2 to a position nearer the bottom of the well bore. The rate oi lowering of the drill string within the bore with corresponding :rovernent of the prospecting instrument is carefully controlled for reasons which will be hereinafter mentioned.

Following the lowering of the drill string within the wel! bore as described, the prospecting instrument is removed therefrom by use o! a suitable fishing device. For this purpose the drill string can be opened either by disengagement of the kelly i5 from the Kelly bar il or by disengaging the Kelly bar from the top stem element. whichever is convenient under theconciitions of operation. Thereafter-the kelly :'S'r'Keily bar. removed during the iishing, is recoupled to the bar or sternrespectiveiy and vdrilling operations can then proceed in the conventional manner.

l-"ollowlng this sequence of operations and the removal oi the prospecting instrument as mentioned, the equipment is disposed within the well bore substantially as illustrated in Figure 3, in readiness for further drilling of the well bore, with the only interruption in the normal drilling -operations occurring at the time oi removal of the instrument. This brief interruption, as a practical matter. is of negligible importance.

The prospective instrument il employed in the practice of this invention as above described is diagrammatically illustrated in Figure 4 and comprises a fluid-tight capsule or envelope 2li, provided at its top end with an irregularlyy shaped projecting member 2i capable of readily engaging with a fishing cable to facilitate removal of the instrument from the drill stem as mentioned. Within the capsule 2B are provided a control unit 22,3, signal transmitter or recorder 23, and a geophysical prospecting device 24, suitably interccnnected and interrelated as will be hereinafter described.

The geophysical prospecting device 2( can be any one of the several types of instluments that are capable of detecting characteristics of nearby geological formations despite the prence of relatively large masses of metal such as the drill stern which. in the practice of this invention, sur. rounds the instrument during use. More particulnrly. the prospecting device can be an instrument for detecting, qualitatively and/or quantitatively, natural. artiiicially induced, or reilected radiation emanating from the neighborlng geological formations under investigation. A typical device for this purpose comprises an ...po-.m

use of the signals from the device to control otherv equipment, particularly recorders or the like. Prospecting devices of this nature are disclosed in the 'iatent No. 2,133,776, granted to John C.v

Bender, October i8, i938, and in the copending applications of Jacob Neufeld, S. N. 161,350, tiled August 27, i937, and S. N. 279,964, filed June 7, 1939. The prospecting device used can also if desired be of a type capable of detecting primary or secondary neutron streams emanating from" geological formations. This type of prospecting instrument is similar in principle and construc tion to that above described except that the ionization chamber is provided with a suitable surfacing material capable, by interaction with' neutron streams, of causing ionization oi the dielectric within the chamber. A typical device of this nature is disclosed in the patent to Folkert Brons, No. 2,220,509, granted November 5, 1940, and in the paient to Robert E. Fearon. No. 2,308,361, June 12, 1943, and in the copending application ci Robert E. Fcarcn, Serial Number` 325.880, filed March 25, 1940.

The prospecting device 26 is connected to a signal transmitter or recording device 23 which includes a means for directly recording signals from the prospecting device upon a time driven sheet, or which comprises e suitable transmitter ci high audible or radio frequency signals capable recording or indicating equipment located at the surface. It is preferred, instead of transmitting the signals to remotely located recording equipment, to record the signals from the geophysical prospecting device within the capsule directly upon a tape or record sheet moved in accordance with motion oi the instrument during use, thus providingv an index of` the character of the formations directly correlated with an indicatioriol the position oi the instrumait. This effect is readily accomplished by driving the tape with a suitable 'ming mechanism imparting uniform rate oi' movement thereto, and lowering the drill string at a uniform rate within the Well bore, permitting comparison ci the rates of movement ci the intrument and the string to give accurate indications of the instrument position. 1f it is desirable to transmit signals from the prospecting device directly to surface indicating or recording equipment, the same can b achieved by using a suitable signal generator controlled by the prospecting device. For example, an audible signal. preferably of high frequency, can be transmitted through the well :nud or through the metallic drill stem, utilizing, if desired, the principles disclosed in the patent to Robert F. Davis, No. 2,285,809, June 12, 1942, or i! preferred a radio signal can he transmitted from the prospecting device to surface equipment, if desired. in accordance with the principles disclosed in the copending applications of Robert E. Fearon, S. N. 311,218 and S.

1939. It will be understood that signals transmitted from the subsurface prospecting instrument to suriace recording equipment, at the time of recording will be correlated with indications oi movement oi the prospecting device stem or .during the time the instrument is being n to a microphone or other suitable receiving de- 'of transmitting the signals irom the prospecting y devicey when within the weil bore to suitable N. 311,219, both tiled December 27, cations from the terxnined time interval thereafter. mechanism also, if desired, can be operated by withdrawn from said position. mechanism can be, ii' desired. a simple time control capable oi causing the recording equipment to operate at a. preselected time for a prede- The control reception of high audible frequency signals transmitted through the drill stem or well mud vice connected with appropriate amplifiers, relays or equivalent mechanism to control the operation of the recording mechanism. Or, if

desired, in like manner, a radio receive capable of detecting signals transmitted from surface equipment can be used to control the operation of the prospecting device. As a further possible modiication, within the scope or the invention, a purely mechanical controlcan be used, if desired, which would cause the recording mechanism to operate when placed in its preselected position within the drili stern and to cease to function when removed therefrom by suitable interengaging members upon the instrument and within the drill stein. A mechanical control, functioningby movement of well mud in the vicinity of the instrument, can"'a'lso be employed to ccntrol the operation of the recording equipment.

From the foregoing description, it will be seen that the present invention provides a method ci' geophysical 'prospecting 'that can be practiced during, and Av:l.o1it interruption of the usual course of well drilling operations, thus providing the drilling crew and operators withl the advantages accruing from immediate knowledge o! the nature oi strata being tr versed oy the bore.

I claim:

1. Method oi' simultaneously drilling and prosl pecting a well bore that comprises the' following sequence of operations: partially withdrawing the drill string from operative position within the well bore; placing a prospecting instrument oi a type capable of measuring radiations which will pass through the drill stem Within the partially withdrawn drill stem near the drill bit: returning the drill string to its original position at a measured rate of movement; removing the prospecting instrument from the dr"l stern; and

correlating indications from the prospecting instrument with measurements of movement of the drill string to obtain indications of the character of formations traversed by the well bore.

2. Method ci geophysical prospecting within a well bore during usual well drilling operations that comprises placing a prospecting instrument of a type capable o! measuring radiations which will pass through the drill stem -Within the base of the drill stem while the drill string is in raised position for addition ci a stem element thereto, returning the string to operative position at a measured rate of movement, removing the lnstrument from the stem after the st turned to arming rnc is re position, and correlating indiprospecting device with uid This control measurements o! the return movement o! the drill string as an indication of the nature of traveried strata.

3. Method o! simultaneously drilling and prospecting a well bore that comprises the following sequence of operations: partially withdrawing the drill string from operative position within the well bore; placing a radiation-sensitive prospecting instrument of a type capable o! measuring radiations which will pass through the drill stem at a preselected position within the partially withdrawn drill stem near the drill bit; returning the drill string to its original position at a measured rate of movement; removing the prospecting instrument from the drill stem: and correlating indications from the prospecting instrument with measurements o movement of the drill string to obtain indications of the character oi' formations traversed .by the well bore. i

4. Method of geophysical prospecting within a well bore during usual well drilling operations that comprises placing a radiation-sensitive prospecting instrument of a type capable of meas.- uring radiations which will pass through the drill stern at a preselected position within the base oi the drill stem while the drill string is in raised position for addition of a stern element thereto, returning the string to operative position at a measured rate ot movement, removing the instrument from the stem after the string is returned to drilling position, and correlating indications from the prospecting device with said measurements of the return movement of the drill string as an indication o.' the nature of traversed strata.

5. Method of simultaneously drilling and prospecting a well bore that comprises the following sequence of operations: partially withdrawing the drill string from operative position within the well bore; placing a highpressure ionization chamber through which a current ows proportional to radiation impinging thereon within the partially withdrawn drill stem near the drill bit: returning the drill string to its original position at a measured rate of movement: measuring the A :estanco 8. Method oi simultaneously drilling and prospecting a well bore that comprises the following sequence of operations: partially withdrawing the drill string from operative position within the well bore: placing a prospecting instrument sensitive to gamma radiationemanating from geo logical formations within the partially withdrawn drill stem near the drill bit; returning the drill string to its original position at a-measured rate of movement; removing the prospecting instrument from the drill stern; and correlating indications from the prospecting instrument with measurements oi movement of the drill string to obtain indications of the character o! formations traversed by the well bore.

7. Apparatus useful in the simultaneous drilling and prospecting o a well bore that comprises a fluid-tight capsule capable oi being placed within an ordinary drill stem, a geophysical prospecting device within said capsule capable oi detecting characteristics of geological formations by measuring radiations which will pass through the drill stem. mans for providing a' record ol indications from said prospecting instrument, and control means within said capsule for regulating operation oi the prospecting devis S. Apparatus useful in the simultaneous drill ing and prospecting of a Well bore that comprises a fluid-tight capsule capable of being placed within an ordinary drill stem, a geophysical prospecting device sensitive to radiation within said capsule capable of detecting characteristics of geological formations by measuring radiations which will pass through the drill `stern, means for providing a record of indications i rom said pros pecting instrument, and control means lwithin said capsule ior regulating operation of the prospecting device.

9. Apparatus useful in the simultaneous drilling and prospecting oi a well bore that comprises a :duid-tight capsule capable of being placed within an ordinary drill stern, a geophysical pros pecting device of the type including a high pressure ionization chamber. sensitive to gamma radiation within said capsule capable of detecting characteristics of geological formations, means for providing a record of indications from said prospecting instrument, and control means within said capsule for regulating operation of the prospecting device.

CHRLES A. MOON. 

